Method of making insulated pull chains



NOV. 2, 1954 WQLD METHOD OF MAKING INSULATED PULL CHAINS Filed Mapch 24,1952 United StatesPatent ()fiice METHOD @F MAKIN G MSULATED PULL CHAINSTrygve Wold, Georgetown, Ontario, Canada, assignor to & Stone Lindted,Toronto, Ontario, Canada, a corporation of Canada Application March 24,1952, Serial No. 278,224

Claims priority, application Canada January 17, 1952 1 Claim. (Cl.29155.52)

This invention has to do with the manufacture of insulators and moreparticularly of insulators of the type used along the length of pullchains for electric switches. These insulators are commonly known assecondary insulators.

insulators of this particular type are used to break the electricalconductivity of pull chains used on electric switches when such switchesare located in a damp room such as a bathroom or basement. The presentpractice concerning the installation of the insulators is such thatconsiderable loss of time and expense is experienced when it isnecessary to use these insulators. Normally, the pull chains are made inthe continuous length and attached to the switch. If an installation ismade in a damp location the chain must be broken and an insulatorinserted between the two broken ends.

This practice has many drawbacks. In the first place, the insulator incommon use is made up of three pieces; an insulating shank, two membersattached to the end of the shank and adapted to engage the ends of thechain. This particular construction necessitates the installation of theinsulator by hand with the consequent loss of time. If the installationis done at home by the householder, the possibility of an insecureinstallation is very great and an insulator so installed may be oflittle or no use when it is needed.

The primary purpose of this invention is to provide a method ofincorporating an insulator in the chain as a unit thereof in such amanner that its insulating properties may be realized to the bestadvantage. Another important object of this invention is to provide forinstalling an insulator in a pull chain economically and quickly usingassembly line production methods.

The insulator to be inserted in a pull chain which is the embodiment ofthis invention is moulded of a plastic material of high tensile strengthand of good insulating qualities. This insulator may be installed singlyin one length of chain to serve as a single pull chain or may be mouldedabout a long length of chain at spaced intervals so as to provide anynumber of pull chains which may be cut from a single length of chain.One feature of the method of the present invention is that the pullchains may be produced from a continuous chain length. It will beappreciated, however, that two separate chain lengths may be joinedtogether with the plastic insulator unit without departing from thespirit and scope of the invention. This method of construction enables amanufacturer to produce a better quality insulator for pull chains moreeconomically than was possible with the previous type of chaininsulators.

Other features and advantages of the invention will be apparent from thefollowing description when read in conjunction with the appendeddrawings in which:

Figure 1 is a perspective view of the insulated chain.

Figure 2 is a sectional view of the insulator and chain.

Figure 3 is a plan view of the insulator and chain.

Figure 4 is a perspective view of the chain with the plastic grippingknobs and the ornamental mouldings attached.

Referring now to the drawings it will be seen that the insulatorcomprises a piece of plastic moulded about the chain 11 and extends in alongitudinal direction over a plurality of links of the chain. Inpractice it has been found satisfactory to have the insulator extendingso as to enclose five links. In the centre of the insulator 10 there isa hole 12 which passes completely through the insulator and breaks thechain. The

purpose of this hole is to provide the required discontinuity in theconductivity of the chain. Various means can be applied to effect theremoval of the link inside the insulator among which are punching a holethrough the insulator or drilling a hole through the insulator orremoving the link prior to moulding the insulator about the broken endsof the chain. if the link is to be removed during the moulding operationan instrument is mounted within the mould which will engage a link ofthe chain and remove it as the mould is being closed and the plasticbeing introduced therein. If the link is to be removed after theinsulator has been moulded about the chain a hole is either drilled orpunched through the insulator to effect the removal of the link. inpractice the removal of the link before the moulding of the insulatoroccurs is not practical as mass production methods are desirable and canonly be effected if a continuous length of chain is used upon which theinsulators are moulded at spaced intervals. After the moulding processis complete the chain may be cut into the appropriate lengths eachlength containing one insulator and these chains installed upon theswitches with which they are to be used.

The moulding operation comprises the placement of a length of chainacross the mould and securing it in that position. The moulds are thenclosed about the chain and the plastic is injected into the mould tocompletely surround the chain and form the insulator. At some timeduring this process a link has been removed from the chain in a positionsuch that the vacant spot left by the removal of the link will be in thecentre of the plastic insulator. The removal of this link can beaccomplished either during, before or after the moulding operation. ifit is accomplished during the moulding operation, then it is removed bya projection on onehalf of the mould which as the mould closes, engagesa length of the chain and forces it against a cutting edge on the otherhalt of the mould thereby breaking the chain and removing a link. if itis accomplished after the moulding operation then it is done by eitherboring or punching a hole through the insulator which removes a link ofthe chain in the process. If it is done before the moulding operationthe chain is broken before it is placed across the mould and the twobroken ends project into the mould from either side leaving a spacetherebetween to provide the required discontinuity in the conductivityof the chain.

In addition to moulding an insulator into the chain as has beendescribed above, it is contemplated by this invention to mould at randomor at predetermined intervals configurations of plastic on the chain forornamental purposes.

It is further contemplated to mould a pull knob at the end of the chainto facilitate the grasping of the chain. This pull knob may be made ofluminously coated or impregnated material to facilitate its location inthe dark. These embodiments of the invention may be seen in Figure 4 inwhich 20 is the pull knob and 21 the ornamental moulding.

It will be obvious from the foregoing description that the inventionallows an insulator to be mass produced with an efficiency and economyfar superior to that possible with insulators made by previous methods.The insulator produced according to the invention cannot be removed fromthe chain as it is moulded as an integral part thereof and is actuallystronger than the chain itself. Its insulating properties are superiorto those of insulators previously used. Various colours can be used inthe manufacture of these insulators in order to provide an insulatorwhich will blend or contrast with the lampholder or other interiordecoration.

In the preferred embodiment of the invention a phenolic formaldihyde ofthe thermosetting type has been found to be most suitable. Thiscomposition possesses high tensile strength together with goodinsulating properties.

I claim:

A method for providing an insulator to electrically insulate one portionof a chain from another portion thereof comprising the steps of moldinga body of insulating plastic about the chain to engage therewith andafter the molding operation removing plastic and chain material so as toform a hole through said plastic body, said hole passing through thepath of the chain and severixlilg it to provide discontinuity in theconductivity of the c am.

References Cited in the file of this patent Number 5 1,104,009 1,419,6441,769,245 2,298,591 2,401,451

UNITED STATES PATENTS Name Date Seguin July 21, 1914 Recker June 13,1922 Tregoning July 1, 1930 Ross Oct. 13, 1942 Arey June 4, 1946

